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BiOI/TiO 2 heterostructures with different Bi to Ti molar ratios were synthesized through a simple soft-chemical method at a temperature as low as 80 °C. The as-prepared powders were characterized by X-ray powder diffraction, electron microscopy, UV−vis diffuse reflectance spectroscopy, nitrogen sorption, and X-ray photoelectron spectroscopy. The photocatalytic activities of these BiOI/TiO 2 heterostructures were evaluated on the degradation of methyl orange under visible-light irradiation (λ > 420 nm). The results revealed that the BiOI/TiO 2 heterostructures exhibited much higher photocatalytic activities than pure BiOI and TiO 2, respectively, and 50%BiOI/TiO 2 showed the best activity among all these heterostructured photocatalysts. Surface photovoltage spectroscopy and transient photovoltage measurements were used to confirm the formation of heterojunction and probe charge transfer between BiOI and TiO 2 . The visible-light photocatalytic activity enhancement of BiOI/TiO 2 heterostructures could be attributed to its strong absorption in the visible region and low recombination rate of the electron−hole pairs because of the heterojunction formed between BiOI and TiO 2 .
Zhang et al. (Wed,) studied this question.